Coal Tar Sealants Pollute Local Waterways and Increase Risk of Cancer

September 29, 2016 – The City of Ypsilanti passed a resolution last week banning the use of coal tar sealants on asphalt.  And they are not the first in Michigan to do so.  Ann Arbor, Van Buren Township, Dexter, Scio Township, Spring Lake Township have all passed similar resolutions.

Coal tar is the most commonly used sealant for asphalt driveways, parking lots, and playgrounds throughout the state, extending the lifespan of these surfaces. Why would communities ban such a sensible product?

Unfortunately, coal tar sealants contain 20 to 35% coal tar pitch, a byproduct of the steel manufacturing industry, which is 50% or more polycyclic aromatic hydrocarbons (PAHs) by weight. PAHs are a group of over 100 chemicals that are persistent organic compounds. Several PAHs are suspected or known human carcinogens. Some cause birth defects. And many are lethal to fish and other aquatic life.

PAHs are also released from burning coal, oil, gasoline, trash, tobacco, and wood.

PAHs from coal tar sealants are released into the environment in several ways. During application, PAHs off-gas into the air, affecting air quality. As the sealant weathers, dust from the pavement makes its way into homes via shoes and clothing. Coal tar dust can also settle in nearby lawns and gardens. The U.S. Geological Survey, partnering with a human-health-risk analyst, found people living adjacent to coal tar sealed surfaces had a cancer risk 38 times higher than those living next to unsealed pavement.

Rainwater washing over coal tar sealed surfaces picks up tiny bits of the sealant and carries the pollutants straight to the nearest river, lake, or stormwater catch basin. Once in our waterways, PAHs sink down to the sediment or bed of the river or lake. Mammals, birds, fish, amphibians, and plants are all affected. Studies have linked PAH exposure in aquatic animals to stunted growth, reduced reproduction, difficulty swimming, liver problems, altered development, immune system impairment and death. Studies find coal tar sealants to be the largest source of PAH contamination to urban waterways.

The  Huron River Watershed Council (HRWC) tested local retention ponds and found elevated concentrations of many PAHs in sediment samples--enough to cause adverse effects in aquatic organisms.

Should we expect crumbling driveways and parking lots in Ypsilanti, Ann Arbor, and other Michigan communities that have enacted a ban? Not necessarily. Other coatings, such as asphalt emulsion sealants, contain a fraction (1/1000) of the PAHs that coal tar sealants do and are readily available in stores and through contractors.

Two states, Washington and Minnesota, have enacted coal tar sealant bans, as have other cities across the country, including Austin, TX and Washington D.C. Major retailers Home Depot, Lowe’s, and Ace Hardware have stopped selling the products for home use. Midwest big box chain, Meijer, takes the cause a step further by not sealing its own parking lots with coal tar—or any other sealant. The Ecology Center encourages other owners of large paved areas to follow Meijer’s lead: forego coal tar sealants and put human health and the health of our local waterways first.


Published on September 28, 2016